fix: allow http client retry when lost response with next_uri=/final.

src/query/service/src/servers/http/v1/json_block.rs

@@ -21,7 +21,7 @@ use databend_common_formats::field_encoder::FieldEncoderValues;
 use databend_common_io::prelude::FormatSettings;
 use serde_json::Value as JsonValue;
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub struct JsonBlock {
     pub(crate) data: Vec<Vec<JsonValue>>,
 }

src/query/service/src/servers/http/v1/query/page_manager.rs

@@ -106,10 +106,13 @@ impl PageManager {
                 Ok(page)
             } else {
                 // when end is set to true, client should recv a response with next_url = final_url
-                Err(ErrorCode::Internal(format!(
-                    "expect /final from client, got /page/{}.",
-                    page_no
-                )))
+                // but the response may be lost and client will retry,
+                // we simply return an empty page.
+                let page = Page {
+                    data: JsonBlock::default(),
+                    total_rows: self.total_rows,
+                };
+                Ok(page)
             }
         } else if page_no + 1 == next_no {
             // later, there may be other ways to ack and drop the last page except collect_new_page.

src/query/service/tests/it/servers/http/http_query_handlers.rs

@@ -305,14 +305,22 @@ async fn test_simple_sql() -> Result<()> {
         assert_eq!(result.state, ExecuteStateKind::Succeeded, "{:?}", result);
     }
 
-    // get page not expected
+    // client retry
     let page_1_uri = make_page_uri(query_id, 1);
-    let response = get_uri(&ep, &page_1_uri).await;
+    let (_, result) = get_uri_checked(&ep, &page_0_uri).await?;
+    assert_eq!(status, StatusCode::OK, "{:?}", result);
+    assert!(result.error.is_none(), "{:?}", result);
+    assert_eq!(result.data.len(), 0, "{:?}", result);
+    assert_eq!(result.next_uri, Some(final_uri.clone()), "{:?}", result);
+
+    // get page not expected
+    let page_2_uri = make_page_uri(query_id, 2);
+    let response = get_uri(&ep, &page_2_uri).await;
     assert_eq!(response.status(), StatusCode::NOT_FOUND, "{:?}", result);
     let body = response.into_body().into_string().await.unwrap();
     assert_eq!(
         body,
-        r#"{"error":{"code":"404","message":"expect /final from client, got /page/1."}}"#
+        r#"{"error":{"code":"404","message":"wrong page number 2"}}"#
     );
 
     // final